The overall objective of this proposed research is to further characterize the functional, hemodynamic, and structural characteristics of unilaterally-diseased kidney models in trained dogs. Studies in part A are designed to further elucidate the exaggerated natriuresis of a diseased kidney (compared to the contralateral control kidney which maintains a non-azotemic environment) following extracellular fluid volume expansion. This exaggerated response, which is a deviation from that predicted by the "intact nephron hypothesis", will be examined in a model of unilateral glomerulo-nephritis presently being developed in our laboratory. In addition, hemodynamic studies (employing Kr85-washout and extraction of PAH), structural studies (employing silicon rubber injections and Hanssen's ferrocyanide technic), and functional studies (employing TM glucose and direct papillary sampling) will be performed to specifically localize the areas of the nephron or the kidney responsible for the foregoing functional derangement. Studies in part B are designed to further elucidate the mechanism of hypertension following unilateral constriction of the renal artery in the presence of a contralateral control kidney. The objective is to demonstrate that by monitoring and controlling renal artery perfusion pressure (by utilizing an inflatable cuff around the renal artery and a chronic indwelling renal artery catheter) that sustained hypertension can be induced in this animal species. Chronic indwelling renal venous catheters and split-bladders will further facilitate measurement of alterations in renal blood flow, renin secretion, and urine formation.